The present invention generally relates to manufacture and assembly of structures using composite materials and, more particularly, to drilling holes at precise locations in a part—such as a composite or metallic aircraft part—and, for safety and health reasons, collecting the debris—such as composite dust or metallic drill chips—generated by the drilling process.
In conventional practice, before a pattern of holes is drilled in a part to be assembled into a structure, a template, or jig, is made and placed on the surface of the part to be drilled. For example, in the aerospace industry, the structure, or assembly, may be a composite aircraft skin over an aluminum substructure. Examples may also be found in the marine and refrigeration industries, such as applications to boat hulls and heating/air conditioning ducts. The template or jig contains holes conforming to the desired hole pattern that is to be made on the surface of the part to be drilled. A drill is then inserted, typically manually by a drill operator, in each hole of the jig and is used to drill a hole into or through the part.
Drill operators in one manufacturing environment have experienced a high rate of ergonomic injuries—such as carpal tunnel syndrome—some of which occur, for example, due to the number of manually drilled holes and the drilling equipment used. Due to the nature of the structure and the capabilities of the tools used, the manual drilling operation for a structure of composite skins over aluminum substructure typically consists of at least four drilling passes, increasing operator exposure to injury with each additional pass. In addition, the drilling process generates particles of material, such as metal and composite debris, from the structure. For example, aircraft skin often includes composite materials—such as carbon and epoxy—which release a dust of fine particles when drilled through. The fine particles are unhealthy when absorbed in the human body. Also, the dust of fine particles may contaminate sensitive equipment and cause reliability problems. For health and safety reasons, operators are required to collect the carbon epoxy dust with a vacuum collection system during the drilling process. Prior art templates generally include a flat plate with a separate vacuum system where the operator or operators must position the template and operate a drill separately from the vacuum system. The separate operation of these systems is generally inefficient for collection of dust particles generated during the drilling process, and the separate operation of these systems further increases operator exposure to a high rate of ergonomic injuries when manually drilling a large number of holes.
For example, the prior art used strip templates that are typically flimsy 0.020–0.030 inch metal strips curved to more or less conform to the surface of the structure to be drilled. Thus, the prior art templates are not made to fit exactly to the mold line surface of the structure, and are generally copied from a master tool, rather than directly from the mold line specifications. The lack of exact of fit to the mold line generally limits the positioning and drilling accuracy of the template. Drill guide bushings, of hardened metal highly resistant to wear, may be used to line the holes of the template and to direct and guide the drill as it passes through the template and into the assembly. The use of drill guide bushings is improved with a thicker jig to grip and hold the bushing without movement throughout the drilling operation and to correctly direct the drill as it passes through the jig and into the structure.
A thicker, more rigid jig or template could also improve clamp-up of the structure. Clamp-up refers to the temporary clamping together, for example, of the skin and aluminum substructure together with the template. Clamp up is commonly achieved in the aerospace industry using pin clamps inserted through a hole that is lined up in the template, skin, and substructure, which grip the template, skin, and substructure and hold them together in the region near the hole during the drilling process. By allowing less relative movement among the template, skin, and substructure, a thicker or more rigid template could improve the stability of the clamp up and thereby improve hole quality. Improved hole quality could, for example, eliminate deburring of the structure after drilling, which typically requires disassembly of the skin and substructure of the structure, so that disassembly of the structure and deburring the structure after drilling could both be eliminated.
As can be seen, there is a need for a template for drilling a pattern of holes in a structure and for collecting debris generated by the drilling process. There is also a need for a drill template with an integral vacuum collection system. Moreover, there is a need for a drill template that has an exact fit to a mold line surface of a structure, that increases positioning and drilling accuracy and reduces the number of passes required to drill a structure. Furthermore, there is a need for a template that also improves the clamp-up of the structure and, thus, improves hole quality and eliminates deburring.